This project is intended to identify and characterize active transposable elements (TEs) in tetraploid cotton. The recent polyploidization of cotton (1-2 million years ago) was likely accompanied by massive genome reorganization, which may have been mediated by the wide spread activation and proliferation of several TEa. Any elements that were mobilized by polyploidization may still be active in existing tetraploid cotton species. The characterization of those elements will provide insight into transposon movement and their relation to polyploid formation. The existence of both tetraploid and diploid cotton species provides a unique organism for this study. The procedures to be incorporated in this project include RT-PCR and Transposon Display (TD). Since retro-elements are generally the most abundant TEs in large genomes, they could likely have the greatest impact on the genomic reorganization that accompanies polyploidization. RT-PCR provides a means of identifying the RNA intermediates that result from each retro-element transposition. Meanwhile, TD allows the following of new or recent transposon movement. The coordination of the two techniques should provide a powerful mechanism of identifying TEs that may have been activated by polyploidization.